Device for measuring camber and caster of vehicle wheels

ABSTRACT

A projector pivotal about an inclined axis casts upon a reflector mounted on a wheel a pattern, in the form of cross hairs, which reflector returns the image to a screen having therein two photo-diodes, the angular movement of the projector required to cause a cross hair to fall across the respective photo-diode is a measure of the caster or camber of the wheel. The projector is connected to the tab of a resistor, the voltage at the tab being indicative of the pivotal movement of the projector.

United States Patent 1191 Schirmer Sept. 4, 1973 DEVICE FOR MEASURINGCAMBER AND [56] References Cited CASTER OF VEHICLE WHEELS UNITED STATESPATENTS [75] Inventor: Giinter Schirmer, Leinfeiden, 3,316,800 5/1967Kibler 356/152 Germany 3,532,892 10/1970 Murphy 356/152 3,533,69910/1970 Hopkins et al... 356/l55 Asslgneer Robert Bosch GmbH, Stuttgart,2,410,339 10/1946 Creagmile 356/155 Germany [22] Filed: Oct. 28 1970Primary Examiner-William L. Sikes Attorney-Michael S. Striker [21] Appl.No.: 84,798

Related US. Application Data ['57] ABSTRCT: [63] Continuatiommpan of47,034, June 17 A PIOJCCtO! pivotal about an mchned axis casts upon a1970, Pat. No. 3,630,623. reflector mounted on a wheel a pattern, in theform of cross hairs, which reflector returns the image to a [30] ForeignApplication Priorit Data screen having therein two photo-diodes, theangular June 1 1969 Germany 19 30 737 0 movement of the projectorrequired to cause a cross hair to fall across the respective photo-diodeis a mea- 52] CL l 356/155 sure of the caster or camber of the wheel.The projec- [51 1 Int. Cl 11/26 tor is connected to the tab of aresistor, the voltage at [58] Field or'555.?..'.'.'..'.'.'I.'I 355/152155 153 the being indicative Piwtal mmemem REGISTERING 1 MEANS.

projector.

11 Claims,'8 Drawing Figures PATENTEDSEP'WB SHEET 1 OF 2 F76 faREGISTERING MEANS mum/r04 Gd'n/er 50mm? 7 /18,; Arrc /w'y DEVICE FORMEASURING CAMBER AND CASTER OF VEHICLE WHEELS This application is aContinuation-in-part of patent application Ser. No. 47,034, filed June17, 1970, and issued Dec. 28, 1971 as U.S. Pat. No. 3,630,623.

BACKGROUND OF THE INVENTION The invention relates to an arrangement formeasuring the angular deviation of at least one wheel means from apredetermined plane relative to the body of a vehicle.

SUMMARY OF THE INVENTION An object of the invention is an improvedarrangement of the aforesaid kind. The invention consists essentially ofprojector means adapted to project an image of measuring indicia towardsthe wheel means, reflector means, mounted on the wheel means to assumethe angular deviation thereof, and mounted in the path of the projectedimage to reflect the image; screen means mounted in the path of thereflected image whereby an optical path is defined between the projectormeans and the screen means, at least one control indicium arranged onthe screen means in such a position that the image of the reflectedindicia is located on the screen means in a predetermined positionrelative to the control indicium when the wheel means is undeviated fromthe predetermined plane; means mounting the projector means tumablyabout an inclined axis to DESCRIPTION OF THE PREFERRED EMBODIMENTS Withreference to FIG. 1, there is mounted on the wheel of a motorvehicle amirror or reflector 11, which is normal to the axle 12 of the wheel 10.An optical projector unit 13, which is mounted free to turn voltage onthe tap 15 is indicative of the angular posienable changing of theposition of the image on the 7 screen means until the image is in thepredetermined position relative to the control indicium of the screenmeans, whereby the extent of .tuming of the projector means is anindication of the angular deviation of the position of the wheel meansfrom the predetermined plane; and an angle measuring circuit forproviding, in dependence on the extent of turning of the projector meansabout the inclined axis, an electrical signal indicating the angulardeviation of the wheel means.

The novel features which are consideredas characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING tor in its first end position;

FIG. lb is a front view of the projection screen;

. FIG. 2a is a side view of the projector when measuring camber;

FIG.'2b is 'a front view of the screen when camber is being measured;

FIG. 3a is a side view of the projector when measuring caster; I

FIG. 3b is a front view of the screen showing the position of the crosshairs when measuring'caster FIG. 4a is a side view of another projectoraccording to the invention; and

FIG. 4b is a front view of the screen showing the differently coloredcross-hairs.

tion of the projector 13. A picture screen 17 in the plane of which isarranged a light-detecting unit comprising photoelements, here; 18, I9,20 and 21, is positioned in front of the projector. Photo-elements l8and 19 constitute a first photoresponsive component of thelight-detecting unit, and photoelements 20 and 21 constitute a secondphotoresponsive component of the light-detecting unit. FIG. 1b shows thescreen 17 as seen from the front, there being projected on the screen animage of an indicium having the form of two perpendicular lines or;cross hairs 22 that are bright if the rest of the projected image isdark and are dark if the rest of the projected image is bright. When theprojector l3is turned about the inclined axle 14, the cross hairs 22 aremoved along the broken line 23. Axle 14 constitutes mounting means formounting the. projector unit tiltable with respect to thelight-detecting unit.

, An arrangement identical to the one just described is also positionedon the other side of the vehicle, the optical axes of the two projectorscoinciding when the projectors are in their normal, unturned, position.

The projector 13, which is shown in FIG. la-in its first end position,is turned about the inclined axle 14 when measuring the angular positionof the wheel 10, the intersection of the cross hairs 22 moving along thebroken line 23. Beginning from its first end position, shown in FIG. la,the projector is turned until, as shown vin FIG.- 2a, the horizontalcross hair falls across the two photo-diodes 20 and2l that lie along ahorizontal line. When this occurs, the voltage on the tap 15 isconducted to a switching means circuit, not shown, which in turnconducts the voltage to a computer or registering means 24, which storesand records i.e. registers the voltage. This voltage isclearly'indicative'of the camber. The switching means SM is aconventional and angular orientation of the projector unit and thusindirectly of the gate which is so designed that if both of thephotodiodes l8 and 19 or 20 and 21 lie in the path of the correspondingcross hair, the voltage on-the tap 15 is conducted to the registeringmeans 24, whereas if only one, orno, photo-diode lies in the path ofthe'corresponding cross hair, the tap 15 is not connected tothe input ofthe registering means 24. The projector 13' is turned further until thevertical cross hair lies across the pair of photo-diodes 18 and 19, thisposition of the projector corresponding to the caster. The voltage onthe tap 15, which is indicative of the caster, is also conducted to thecomputer 24. The projector positioning motor 25 can return the projectorto its first end position, or continue to turn the projector in the samedirection until it reaches its second end position. These movements ofthe projector by the motor 24 can be controlled by limit'switches.Conversely, once the camber and caster have been measured, a signal canbe gener ated that shuts off the motor 25.

The two pairs of photo-diodes l8, l9 and 20, 21 respectively lie alongvertical and horizontal lines that intersect at a line extended from theoptical axis of the projector, when the latter is in its normal,unturned position.

The arrangement of the invention can be made still simpler by providingtwo photo-diodes instead of four, each photo-diode lying along arespective horizontal and vertical line, these two lines intersecting ata line extended from the aforesaid optical axis of the projector. Thispossibility is shown in FIGS. 4a and 4b. The two hairs of the crosshairs must be'different colors, the two photo-diodes being provided withsuitable color filters 18a and 2a, so that each photo-diode produces asignal only when the corresponding cross hair lies across it. When across hair lies across the corresponding photo-diode (for example, thevertical cross hair across that photo-diode located along the verticalline) a switch means S.M., such as a gate, connects the voltage of thetab to the input of the registering means 24. In the illustratedembodiments, screen 17 itself constitutes means for limiting the rangeof pivoting movement of projector 13.

ln a still further embodiment of the invention, there are provided twophoto-diodes, each photo-diode having a light sensitive surfaceextending in the direction of the line (horizontal or vertical) alongwhich the respective photo-diode is located. in this embodiment, thatphoto-diode located along the vertical line produces a signal when thevertical cross hair lies across it, and that photo-diode located alongthe horizontal line produces a signal when the horizontal cross hairlies across it.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied ina'device for measuring camber and caster of the vehicle wheels, it isnot intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can.

by applying current knowledge readily adapt it for various applicationswithout omitting features that, from the standpoint of prior art, fairlyconstitute essential characteristics of the generic or specificvaspectsof this invention and, therefore, such adaptations should and areintended to be comprehended within the meaning and range of equivalenceof the following claims.

What is claimed as new'and desired to be protected by Letters Patent isset forth in the appended claims. I claim: I 1. An arrangement formeasuring the angular deviation of an object, particularly a vehiclewheel, from a predetermined orientation comprising, in combination, areflector mounted on said object in such a manner as to assume theorientation of said object; a projector unit for projecting an image ofan indicium towards said reflector; a light-detecting unit for receivingfrom said reflector the reflection of said image of an indicium;mounting means mounting one of said units tiltable with respect to theother of said units through a range of tilting movement including, foreach angular deviation of said object, a respective tilted orientationfor which said image of said indicium falls upon said light-detectingunit; registering means for automatically registering the angularorientation of said one of said units when said image of said indiciumfalls upon said lightdetecting unit.

2. An arrangement as defined in claim 1, wherein said mounting meanscomprises means mounting said projector unit for pivotable movementabout a pivot axis inclined with respect to the horizontal.

3. An arrangement as defined in claim 1, wherein said projector unitcomprises means for projecting .an image of an indicium having the formof two intersecting lines.

4. An arrangement as defined in claim 2, wherein said light-detectingunit comprises a first photoresponsive component responsive to a firstrange of light wavelengths and a second photoresponsive componentresponsive to a second different range of light wavelengths, and whereinsaid first and second photoresponsive components are located in a commonvertical plane, and wherein said projector unit has an optical axisintersecting said plane,-and further wherein said first photoresponsivecomponent is located on a vertical line intersecting said opticalaxisand wherein said second photoresponsive component is located on ahorizontal line intersecting said optical axis, and wherein saidprojector unit comprises means for projecting an image of an indiciumhaving the form of two intersecting lines of difi'erent colorsrespectively falling in said first and second ranges of lightwavelengths.

5. An arrangement as defined in claim 4, wherein said first and secondphotoresponsive components each include a respective color filter.

6. An arrangement as defined in claim 2, wherein said projector unitcomprises means for projecting an image of an indicium having the formof two intersecting perpendicular lines, and wherein said lightdetectingunit comprises first and second photoresponsive components located in acommon vertical plane, and wherein said projector unit has an opticalaxis intersecting said plane, and further wherein said firstphotoresponsive component is located on a vertical line intersectingsaid optical axis and has an overall effective length along saidvertical line greater than the effective width of said first componenttransverse to said vertical line, and wherein said secondphotoresponsive component is located on a horizontal line intersectingsaid optical axis and has an overall effective length along saidhorizontal line greater than the effective width of said secondcomponent transverse to said lines upon the two photoelements of therespective one of said photoresponsive components.

10. An arrangement as defined in claim 2, and further including meansfor limiting the range of pivotingmovement of said projector unit aboutsaid pivot axis.

11. An arrangement as defined in claim 2, and further including motormeans for moving said projector unit about said pivot axis.

1. An arrangement for measuring the angular deviation of an object,particularly a vehicle wheel, from a predetermined orientationcomprising, in combination, a reflector mounted on said object in such amanner as to assume the orientation of said object; a projector unit forprojecting an image of an indicium towards said reflector; alight-detecting unit for receiving from said reflector the reflection ofsaid image of an indicium; mounting means mounting one of said unitstiltable with respect to the other of said units through a range oftilting movement including, for each angular deviation of said object, arespective tilted orientation for which said image of said indiciumfalls upon said light-detecting unit; registering means forautomatically registering the angular orientation of said one of saidunits when said image of said indicium falls upon said light-detectingunit.
 2. An arrangement as defined in claim 1, wherein said mountingmeans comprises means mounting said projector unit for pivotablemovement about a pivot axis inclined with respect to the horizontal. 3.An arrangement as defined in claim 1, wherein said projector unitcomprises means for projecting an image of an indicium having the formof two intersecting lines.
 4. An arrangement as defined in claim 2,wherein said light-detecting unit comprises a first photoresponsivecomponent responsive to a first range of light wavelengths and a secondphotoresponsive component responsive to a second different range oflight wavelengths, and wherein said first and second photoresponsivecomponents are located in a common vertical plane, and wherein saidprojector unit has an optical axis intersecting said plane, and furtherwherein said first photoresponsive component is located on a verticalline intersecting said optical axis and wherein said secondphotoresponsive component is located on a horizontal line intersectingsaid optical axis, and wherein said projector unit comprises means forprojecting an image of an indicium having the form of two intersectinglines of different colors respectively falling in said first and secondranges of light wavelengths.
 5. An arrangement as defined in claim 4,wherein said first and second photoresponsive components each include arespective color filter.
 6. An arrangement as defined in claim 2,wherein said projector unit comprises means for projecting an image ofan indicium having the form of two intersecting perpendicular lines, andwherein said light-detecting unit comprises first and secondphotoresponsive components located in a common vertical plane, andwherein said projector unit has an optical axis intersecting said plane,and further wherein said first photoresponsive component is located on avertical line intersecting said optical axis and has an overalleffective length along said vertical line greater than the effectivewidth of said first component transverse to said vertical line, andwherein said second photoresponsive component is located on a horizontalline intersecting said optical axis and has an overall effective lengthalong said horizontal line greater than the effective width of saidsecond component transverse to said horizontal line.
 7. An arrangementas defined in claim 2, wherein said registering means is electrical, andfurther including transducer means for generating an electrical signalindicative of the angular orientation of said projector unit, and switchmeans operative for transmitting said signal to said registering meanswhen said image of said indicium falls upon said light-detecting unit.8. An arrangement as defined in claim 6, wherein said firstphotoresponsive component comprises two discrete photoelements locatedon said vertical line on opposite sides of said optical axis, andwherein said second photoresponsive component comprises two discretephotoelements located on said horizontal line on opposite sides of saidoptical axis.
 9. An arrangement as defined in claim 8, wherein saidregistering means is electrical and further including transducer meansfor generating an electrical signal indicative of the angularorientation of said projector unit, and switch means connected betweensaid registering means and said transducer means and operative fortransmitting said signal to said registering means in response to thefalling of one of said perpendicular lines upon the two photoelements ofthe respective one of said photoresponsive components.
 10. Anarrangement as defined in claim 2, and further including means forlimiting the range of pivoting movement of said projector unit aboutsaid pivot axis.
 11. An arrangement as defined in claim 2, and furtherincluding motor means for moving said projector unit about said pivotaxis.